Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids

Abstract

Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids.

The Viscosity of Nanofluids: A Review of the Theoretical, Empirical, and Numerical Models

“…[76,127]. Few of these works focused on the viscosity of nanofluids and recently there has been some new development in the experimental field, as researchers are now investigating the thermal diffusivity and electrical conductivity of nanofluids and how these properties affect thermal properties [128,129]. For consistency in this review, the following are the experimental works done on the viscosity of nanofluids:…”

“…(49) and the critical zeta potential (ζcritical), which defines the critical surface charge, is also affected by volume concentration [129]. The effect of volume loading is such that the value of zeta potential is moved from below critical to above critical, i.e.…”

“…The effect of volume loading is such that the value of zeta potential is moved from below critical to above critical, i.e. ζ < ζcritical -ζ > ζcritical, consequently, there is a reduction in the electrical conductivity or sometimes a reduction to plateau [129].…”

Factors affecting the pH and electrical conductivity of MgO–ethylene glycol nanofluids

“…At room temperature the electrical conductivity value of the EG used in this experiment was 0.11 μS cm -1 , which totally disagree with the 1.07 μS cm -1 reported by Sarojini et al 28 but comparable to the value of other glycol. 36 The reason for this disparity could lie in the purity of the EG used in these two experiments. In the present experiment, the EG had 99.5% purity while Sarojini et al 28 did not provide the detail of the purity of their EG base fluid.…”

“…30 Also, understanding the electrical conductivity evolutions is particularly vital for lab-on-chip and electrophoretic applications, especially for suspensions with thick EDL, which is typical of salt-free medium, such as ethylene glycol (EG) and propylene glycol (PG). 36 Other emerging areas of applications of nanofluids could be: (i) in medicine, for targeted treatment of malignant cells without damaging healthy tissues, (ii) in biomedical, for drug delivery for some special cases and (iii) in surgery in order to increase the chances of survival of patients. [42][43][44][45][46] As discussed earlier, stability can be achieved with pH modification which is usually monitored by measuring the zeta potential.…”